In recent years, so-called IC cards, in which an integrated circuit element such as a microcomputer, a memory or the like is installed on or incorporated in a plastic card, have been offered for actual use.
Since these IC cards are large in storage capacity and are excellent in crime prevention ability as compared with magnetic stripe cards which have already been in daily use, it has been considered that IC cards can be employed not only in place of conventional magnetic stripe cards, but also for various usages such as identification cards and so on.
By the way, the IC card is arranged such that an integrated circuit device having terminals for connection to an external device such as a reader/writer is mounted in a card made of plastics such as polyvinyl chloride or the like. The integrated circuit device is required to be formed as thin as possible.
There are many types of IC cards but it has been considered in the ISO (International Standardization Organization) that the IC cards should be standardized to a size identical with the conventional magnetic stripe card.
The conventional IC card and an integrated circuit device used in the card will be described below with reference to the accompanying drawings.
FIG. 10 is a perspective view of the IC card, FIG. 11 is a cross-sectional view taken along the line A--A' in FIG. 10, showing the periphery of the integrated circuit device, and FIG. 12 is a longitudinal cross-sectional view of the integrated circuit device which employs the conventional circuit board.
Conventionally, many methods have been carried into effect for a manufacturing method and an arrangement of IC cards. For example, as shown in FIGS. 10 and 11, a well 2 corresponding in size to an integrated circuit device 30 is formed in a thin plastic card 1 in the form of a sheet having a thickness on the order of 760 .mu.m, by the use of an end mill, a Thomson mold or the like. The integrated circuit device 30 having a thickness slightly smaller than the plastic card 1 is inserted in the well 2, and is fixedly bonded to the bore 2 with external connecting terminals 32 being exposed.
The conventional integrated circuit device 30 has been arranged as illustrated in FIG. 12, and as disclosed in U.S. Pat. No. 4,264,917. Circuit conductors such as an external connecting terminal pattern 32, a circuit pattern 33, through-holes 34 and so on are formed on or in an insulating substrate 31 in the form of a film, thereby forming a thin-type circuit board 31A. Each integrated circuit element 35 is die-bonded to the thin-type circuit board 31A, and input/output electrodes of the integrated circuit element 35 and the circuit pattern 33 are connected to each other through metal wires 36 by a wire-bonding system or the like. Further, a sealing frame 37 for stopping flow of resin at resin sealing is provided so as to be bonded to the thin-type circuit board 31A. The integrated circuit elements 35 are sealed by a sealing material 38 such as epoxy resin or the like, to form the integrated circuit device 30.
By the way, the integrated circuit device 30 installed on an IC card has been required to have high reliability and high precision in dimensions and to be low in cost, simultaneously with being thin. In the aforesaid integrated circuit device 30, however, the thin-type circuit board 31A has the following problems in use, because the thin-type circuit board 31A is a two-sided circuit board with through-holes, in which the circuit conductors are formed on both sides of the insulating substrate 31 and are connected to each other through the through-holes 34.
Since the IC cards are required to have a thickness of 760.+-.80 .mu.m similar to conventional magnetic stripe cards, the thickness of the integrated circuit device 30 to be embedded is restricted by a large degree. For example, in case of an IC card arranged such that the integrated circuit device 30 is embedded in the plastic card 1 as shown in FIG. 11, the integrated circuit device 30 embedded in the well 2 is required to be restricted to a thickness of 650.+-.30 .mu.m, should the thickness of the remaining portion A of the bottom of the well 2 in the plastic card 1 be, for example, 110.+-.50 .mu.m including adhesive. As the basic dimensions determining the thickness of the integrated circuit device 30, the dimension B of the thin-type circuit board 31A including the sealing frame 37 illustrated in FIG. 12 becomes very important. Therefore it is necessary for manufacture of the thin-type circuit board 31A such that the dimension B is brought to a value within a certain dimension range, for example, a value within a range of 650.+-.30 .mu.m. However, it is extremely difficult to manufacture such highly accurate and precise thin-type circuit board 31A, resulting in the thin-type circuit board 31A which is high in cost. As a result, for the integrated circuit device 30 having installed thereon the thin-type circuit board 31A it is also difficult to obtain highly accurate thickness dimension, causing a high cost.